I've found two in the span of 10 turns but that was it, and the most in any game yet. Really, if anything, there should be more remains around, even dozens if not hundreds of ships, space stations, refridgerated foodstuffs.
Just think yourself lucky and destroy the enemy

I dont think they had money space encounters in gal civ one

I encountered the same bug (assuming it is one). I was right next to a sprawling Arcean empire and straggling in Military, and as luck would have it I got a free Ranger with absurd stats compared to everything else in the game (something like 24/17 when everything else was max of 8/3). Then next turn, I got another. And another. And another...

I won that game by military

Hmmm, you know I'd forgotten that I'd chosen 'lucky' as an attribute. That could explain some of the frequency. I guess what caught me off-guard was that for the longest time I went without any events at all and then suddenly there was this bloom of ranger ships. I also was nearby the Ancaran (sp) empire and was lagging militarily. Funny story actually, I was also waaaay behind on tech because I'd gone to war on the Thalans (sp). So suddenly I learned that those chipmunk aliens had stolen all of the Ancaran tech and so I traded the chipmunks earth in exchange for technological equality (got all the techs). Earth was a high price but the next turn I conquored the Thalan homeworld and so that worked out ok.

Well, the way I (an evil ruler I am I am) look at it, the most fit and capable of Earth's population had already gone to the Thalan homeworld to fight for my glory. The only people left behind would have been the old, sick, etc. and what better food source be gifted to Earth's new overlords eh? The best and brightest of Earth get a new home and the best tech the galaxy has to offer - it's win-win!

Well, I set the game to 'normal' difficulty but then I do have the 'lucky' trait so that might play into it. The frequency still seems pretty off though - nothing for a long while then a flood and all.

I've got no idea what is a 'good' frequency for these things to come up, but I'm playing a lucky, universalist empire and I'm up to lucky ranger #5. I can't complain, really, since they really boost my military effectiveness (despite the fact that the ships are so slow - I mean, come on, who builds ships that can only move three spaces a turn?).